Background: Tamoxifen is used in endocrine treatment of breast cancer to inhibit estrogen signaling. A set of strati‐ ed ER‐positive and ER‐negative tumor sections was subjected to manual deposition of tamoxifen solution in order to investigate its spatial distribution upon exposure to interaction within thin tissue sections.

Methods: The localization of tamoxifen in tumor sections was assessed by matrix assisted laser deposition/ioniza‐ tion mass spectrometry imaging. The images of extracted ion maps were analyzed for comparison of signal intensity distributions.

Background: Tamoxifen is used in endocrine treatment of breast cancer to inhibit estrogen signaling. A set of strati‐ ed ER‐positive and ER‐negative tumor sections was subjected to manual deposition of tamoxifen solution in order to investigate its spatial distribution upon exposure to interaction within thin tissue sections.

Methods: The localization of tamoxifen in tumor sections was assessed by matrix assisted laser deposition/ioniza‐ tion mass spectrometry imaging. The images of extracted ion maps were analyzed for comparison of signal intensity distributions.